The present invention relates generally to lift mechanisms for a dental chair and more particularly to a parallelogram lift having means for reducing the horizontal component of motion produced by the parallelogram lift.
It is preferred in any dental chair that the chair be lifted in a straight vertical path, however, where a parallelogram lifting arrangement is used, the operation of the lift imparts not only a vertical, but also a horizontal component of motion so that the chair can be said to "travel" horizontally as it is raised or lowered. Various methods have been employed in the parallelogram lifts of dental chairs to compensate for this horizontal component of motion. For example, one such arrangement shown in U.S. Pat. No. 3,804,460 employs a double parallelogram linkage so that as the chair is raised, the forward horizontal component of one of the parallelogram linkages is compensated by a rearward horizontal component of motion of the second parallelogram linkage. Another arrangement of a double parallelogram linkage is shown in U.S. Pat. No. 3,807,680. Other chairs employ a motorized system, wherein, a separate drive motor is used to translate the chair with respect to the parallel motion linkage to compensate for any horizontal component of motion.
In the present invention a single link operatively connected to the parallel motion linkage and the seat of the dental chair acts to move the seat counter to the horizontal motion imparted by the parallel motion linkage.